In a source/drain region on a silicon substrate in a semiconductor device such as a MOSFET, a thin-film including an alloy of a metal and silicon (silicide) is formed on the substrate for formation of a metal/semiconductor junction. The silicide alloy film is formed in the following manner: a metal thin-film is deposited on the substrate by a sputtering method or the like, and a heat treatment is performed, so that silicon is diffused into the metal thin-film to silicify the metal thin-film.
As for the configuration of such a silicide alloy film, titanium silicide (C54 TiSi2) and cobalt silicide (CoSi2) have been generally known previously. However, these silicides are disilicides in which two Si atoms are combined with one metal atom, and thus these silicides involve a relatively large Si consumption. In recent years, an attempt has been made to make the junction depth extremely small in a source/drain region for attaining further miniaturization and thinning in a semiconductor element such as a MOSFET. Application of a silicide that involves a small Si consumption in silicidation is promising for meeting the above-mentioned requirement.
As a silicide capable of meeting the above-mentioned requirement, nickel silicide (NiSi) is used. NiSi is a monosilicide that involves a small Si consumption when formed, has the advantage of low specific resistance, and is therefore expected to be the mainstream of silicides in future.